Respect The Fatigue Wake

"All workouts leave a fatigue 'wake,' meaning they produce fatigue which will affect subsequent workouts to one degree or another. The effects of fatigue are specific. This means that, for example, the fatigue waks caused by a leg workout will have a more negative effect on a subsequent leg workout than it would have on a subsequent upper-body workout. Similarly, the fatigue wake from an aerobic workout will have a greater effect on a aerobic workout than it would have on an anaerobic workout."
(From Muscle Logic, p.p. 43):